What is cancer?

Did you know that cancer isn’t one disease but more than 100? And depending how you classify cancer, you could even say that there are more than 200 types.

All types of cancer start in our cells. Our bodies are made up of trillions of cells grouped together to form tissues and organs such as muscles, bones, the lungs and the liver. Genes inside each cell tell it when to grow, work, divide and die. Normally, our cells follow these instructions and we stay healthy. But sometimes the instructions get mixed up, causing our cells to grow and divide out of control or not die when they should. As more and more of these abnormal cells grow and divide, they can form a lump in the body called a tumour.

Are all tumours cancer?

No. Some types of tumours are non-cancerous (benign). Non-cancerous tumours have cells that stay in one place and don’t spread. But these tumours can still get quite big. Non-cancerous tumours also don’t usually come back after they are removed.

Other types of tumours are cancerous (malignant). Cancerous tumours can grow into nearby tissues and spread to other parts of the body. This happens when cancer cells get into the blood or lymphatic system. Even when a cancerous tumour is removed, cancer can still come back because cancer cells might have already spread from the tumour to other parts of the body.

It’s important to find cancer as early as possible, when it is usually smaller and easier to treat and there’s less chance that the cancer has spread.

If bladder cancer spreads to the lung, is it called lung cancer?

No. Cancers are named after the part of the body where they start. For example, cancer that starts in the bladder is called bladder cancer. When bladder cancer spreads to the lung, the cancer in the lung is still made up of bladder cancer cells. The new tumours in the lung are lung metastases. So it’s called bladder cancer with lung metastases.

Cancer that has spread to the lung from another part of the body might also be called secondary lung cancer. If cancer starts in the lung, then it is called lung cancer or primary lung cancer.

Often one of the first signs that cancer has spread (metastasized) is swelling in lymph nodes, like those in the neck, underarm or groin area. But cancer can spread almost anywhere in the body.

Solid tumours versus blood cancers

Many types of cancer form solid tumours (lumps) but some do not. Blood cancers, like leukemias, are different from other types of cancer since the cancer cells tend to build up in the blood and bone marrow but may not form lumps. Because the cancer cells are already circulating in the blood, blood cancers are often more widespread throughout the body when they are diagnosed.

How cancers are named

Most cancers are named after where they start in the body, like breast cancer or prostate cancer. But other cancers have scientific names like leukemia, lymphoma and myeloma. And some types of cancer are named after the person who first discovered them – like Hodgkin lymphoma and Wilms tumour (a type of kidney cancer that affects children).

Cancers are also named after the type of tissue that they start in.

Carcinoma

Carcinoma is a cancer that begins in the skin or in tissues that line or cover organs. This lining is called epithelium and is made up of different types of cells. Carcinomas are the most common type of cancer. Examples of carcinomas are:

Adenocarcinomas develop in gland cells like those of the intestines, lung or prostate.

Basal cell carcinoma develops in the skin.

Squamous cell carcinomas develop in the skin and mucous membranes like those lining the mouth and vagina.

Transitional cell carcinomas develop in the urinary system in organs like the bladder and ureters.

Sarcoma

Sarcoma is a cancer that starts in connective or supportive tissues such as bone, muscle, fat, cartilage or blood vessels. Sarcomas are rarer than carcinomas. Examples of sarcomas are:

angiosarcoma

osteosarcoma

chondrosarcoma

liposarcoma

myosarcoma

Melanoma

Melanoma is a type of cancer that starts in cells called melanocytes. These cells make melanin (a pigment that gives skin its colour). Most melanomas develop on the skin but can also develop in any part of the body that has melanocytes like the anus or eyes.

Blood cancers

Leukemia, lymphoma and multiple myeloma are types of blood cancer.

Leukemia

Leukemia starts in the bone marrow where blood cells are made. A person with leukemia has many abnormal blood cells in the bone marrow and blood. This type of cancer does not form a solid tumour.

Lymphoma

Lymphoma is a cancer that starts in lymphocytes. Lymphocytes are types of white blood cells that are part of the immune system and lymphatic system. A person with lymphoma has many abnormal lymphocytes that build up in the lymph nodes, lymph vessels, bone marrow, spleen and other parts of the body.

Multiple myeloma

Multiple myeloma is a cancer of plasma cells, a type of white blood cell made in the bone marrow. Plasma cells are part of the immune system and make antibodies to fight infection. A person with multiple myeloma has many abnormal plasma cells (called myeloma cells) that build up in the bone marrow. Myeloma cells may form tumours in bone or other tissues.

lymphatic system

The group of tissues and organs that produce and store cells that fight infection and diseases.

The lymphatic system includes the adenoids, tonsils, spleen, thymus, lymph nodes, lymph vessels and bone marrow.

Also called the lymph system.

immune system

The complex group of cells and organs that defend the body against infection, disease and foreign substances.

antibody

A type of protein made by the immune system that disarms or destroys a specific foreign substance (antigen) when it appears in the body.